Method and apparatus for managing the allocation of items to processing stations in an order fulfillment process

ABSTRACT

Various embodiments of a method and apparatus for managing the allocation of items to processing stations in an order fulfillment process are described. The apparatus for managing the allocation of items to processing stations in an order fulfillment process may include a conveyance mechanism including at least one item inducted into the conveyance mechanism. The apparatus for managing the allocation of items to processing stations in an order fulfillment process may also include an item allocation component. The item allocation component may be configured to assign the item to a particular sorting station of a group of multiple sorting stations. The item allocation component may determine the particular sorting station to which the item is assigned based upon a determined quantity of other items located at the particular sorting station and a determined quantity of other items en route to the particular sorting station.

This application is a divisional of U.S. patent application Ser. No.12/211,538, filed Sep. 16, 2008, now U.S. Pat. No. 8,952,284, which ishereby incorporated by reference in its entirety.

BACKGROUND

In a distribution system, a retailer or other product distributor (whichmay collectively be referred to as distributors) typically maintains aninventory of various items at one or more distribution centers,fulfillment centers, cross-docking facilities, materials handlingfacilities or warehouses (which may collectively be referred to hereinas materials handling facilities). The inventory items are ordered fromone or more vendors, received at the materials handling facilities asinbound shipments, and stocked in inventory of the materials handlingfacilities. In an order fulfillment process, orders for items may bereceived from customers of the distributor. Units of the ordered itemsare picked from various locations in the inventory in the materialshandling facilities, processed for shipping, and shipped as outboundshipments to the customers.

The order fulfillment process may include a sortation process, in whichmixed units picked for orders are sorted into their respective orders.For example, requests (e.g., orders) for items from requestors may bedivided among multiple pickers, who then pick the items. The orders maybe subdivided among the pickers; therefore, two or more of the pickersmay pick items for one order. Consequently, a sort operation to selectthe proper units of items for given orders from the aggregations ofunits items returned by each respective picker is required.Conventionally, sorting may be performed using automated sortingmechanisms or manual sorting systems. Automated sorting mechanisms forsorting certain types of inventory items according to individual ordersinclude, but are not limited to, the Crisplant® sorter, Eurosort®sorters, and automated sorting mechanisms offered by other vendors.Using an automated sorting mechanism, a stream of incoming picked itemsfor multiple different customer orders are received at the automatedsorting mechanism and sorted by the automated mechanism according toindividual orders.

In typical automated sorting mechanisms, individual units of items areinducted from picked mixed items directly onto the sortation mechanisminto carriers (e.g., tilt trays) that are fixed to the sortationmechanism. Thus, typical automated sorting mechanisms that are used inmaterials handling facilities tend to be linear sorting systems. Linearsorting inducts or places individual units of items from picked items(referred to as singulation) onto an individual tray or transportmechanism that is a fixed component of a linear piece of automatedequipment. All of the trays or transport mechanisms are connected in alinear sequence (typically in a circle or oval continuously-runningloop). An item is placed directly onto a carrier of the automatedsorting mechanism. Linear sorting systems thus tend to be limited invelocity, total capacity, and the size and types of items that can besorted.

Linear automated sorting mechanisms are typically expensive in both costand floor area. Existing linear automated sorting mechanisms tend to notbe flexible, and typically do not scale well as inventory throughputdemands increase, since implementing a fractional solution is oftenimpractical if not impossible. For example, to address a 30-40% increasein order throughput requirement may require purchasing an entire newsorting mechanism, effectively doubling throughput capacity despiteleaving 60-70% of the new capacity unutilized, while also taking up atleast twice as much floor space.

Shoe Sorters and Item Gridlock

The sliding shoe sorter is a high-speed automated sortation system forchanneling and sorting medium size items, totes, and cartons. Operatingat speeds up to 427 fpm, some shoe sorters can process as many as 9,000pieces per hour depending on load length. Bi-directional shoes allowitems to be offloaded from a sequence of moving items (e.g., in acontinuously-running loop) to both sides of the sorter, improving spaceefficiency while providing greater design flexibility. However, if suchoffloading occurs at an insufficient rate, the shoe sorter may becomegridlocked (e.g., unable to accept additional items for induction intothe sorter) due to the quantity of items on the sorter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a logical representation or view of the operation ofa materials handling facility in which embodiments of the non-linear,unit-level sortation system may be implemented.

FIG. 2 illustrates an example of a physical layout of a materialshandling facility, such as an order fulfillment facility or center, inwhich embodiments of the non-linear, unit-level sortation system may beimplemented.

FIG. 3 illustrates an exemplary physical layout of a materials handlingfacility, such as an order fulfillment facility or center, in which anembodiment of the non-linear, unit-level sortation system isimplemented.

FIG. 4 illustrates an exemplary conveyance receptacle according to oneembodiment.

FIG. 5 illustrates operation of an exemplary singulation stationaccording to one embodiment.

FIG. 6 illustrates operation of an exemplary sorting station that may beused in embodiments of the non-linear, unit-level sortation system.

FIGS. 7A and 7B illustrate a side view and a top view, respectively, ofan exemplary sorting station and associated order processing stationsaccording to one embodiment.

FIGS. 8A through 8E illustrate exemplary configurations for ordersorting bins which may be used in various embodiments.

FIG. 9 is a flowchart illustrating a method of operation in anon-linear, unit-level sortation system according to one embodiment.

FIG. 10 is a block diagram illustrating a portion of an orderfulfillment center as well as an item allocation component according toone embodiment.

FIG. 11 is a flowchart illustrating an example method for assigning ordirecting items to particular stations with an order fulfillment centeraccording to one embodiment.

FIG. 12 is a flowchart illustrating an example method for assigning ordirecting items to particular stations with an order fulfillment centeraccording to one embodiment.

FIG. 13 is a block diagram illustrating an exemplary embodiment of acomputer system.

While various embodiments are described herein by way of example forseveral embodiments and illustrative drawings, those skilled in the artwill recognize that various embodiments are not limited to theembodiments or drawings described. It should be understood, that thedrawings and detailed description thereto are not intended to limitembodiments to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents and alternativesfalling within the spirit and scope of various embodiments as defined bythe appended claims. The headings used herein are for organizationalpurposes only and are not meant to be used to limit the scope of thedescription or the claims. As used throughout this application, the word“may” is used in a permissive sense (i.e., meaning having the potentialto), rather than the mandatory sense (i.e., meaning must). Similarly,the words “include,” “including,” and “includes” mean including, but notlimited to.

DETAILED DESCRIPTION OF EMBODIMENTS

Various embodiments of a method and apparatus for managing theallocation of items to processing stations in an order fulfillmentprocess are described. A flexible, non-linear, unit-level sortationsystem is also described which facilitates the sortation of individualunits of items, picked from discrete inventory locations within amaterials handling facility, into orders to fulfill requests fromcustomers. In embodiments, a picking process delivers batches, or astream, of unsorted items for fulfilling requests to one or moresingulation stations. At a singulation station, individual units ofitems are pulled or selected from a mixed collection of items,associated with particular conveyance receptacles, and placed into thereceptacles, with one and only one unit per conveyance receptacle. Theconveyance receptacles are inducted into a conveyance mechanism underthe direction of a control system, which then, through various controlmechanisms, directs the conveyance receptacles to particulardestinations within the materials handling facility. As will bedescribed below, in one embodiment, a destination may be a sortingstation, where the individual items may be manually or automaticallyretrieved from the conveyance receptacles and manually or automaticallyplaced into locations (e.g., slots or bins) corresponding to particularrequests (e.g., customer orders). Once a conveyance receptacle isemptied at its destination, the conveyance mechanism may, but does notnecessarily, return the conveyance receptacle to a singulation station.

To prevent inefficiencies and undesirable situations, such as thegridlock of conveyance receptacles on conveyance mechanism 200, theflexible, non-linear, unit-level sortation system may include an itemallocation component configured to dynamically allocate items (and/orthe conveyance receptacles that carry such items) to various sortingstations within the order fulfillment center.

In linear sortation systems, individual items are inducted to or placedon an individual tray or transport mechanism that is a fixed componentof a linear piece of automated equipment. All of the fixed trays ortransport mechanisms are connected in a linear sequence. A unit of anitem is placed directly on the sorting mechanism. The linear sequencingand fixed trays/transport mechanisms of linear sortation systems limitthe speed of the equipment, the types of products that can be placed onthe system, and the overall total capacity of the system. Theselimitations may result in significant costs for both equipment and laborto operate linear sortation systems.

In embodiments of the non-linear, unit-level sortation system, each unitof an item is placed into a single “floating” tray, container, or tote(referred to herein as a conveyance receptacle). The conveyancereceptacle is associated with a receptacle identifier that uniquelyidentifies the conveyance receptacle in the materials handling facility.For example, each conveyance receptacle may be marked with a bar code orRadio Frequency Identifier (RFID). An item placed into a conveyancereceptacle is associated with the conveyance receptacle, for example byreading or scanning an item identifier from the item and the receptacleidentifier from the receptacle. Conveyance receptacles are described as“floating” because of their non-linear relationship to each other and toautomated equipment. Conveyance receptacle are not fixed to or fixedcomponents of any automated equipment, and each conveyance receptaclehas a non-linear relationship to other conveyance receptacles active inthe system (i.e., there is no necessary ordering of conveyancereceptacles). Conveyance receptacles may be removed from or added to thenon-linear, unit-level sortation system, and may be arbitrarily arrangedon the sortation system. Conveyance receptacles may be removed from oradded to the non-linear, unit-level sortation system at variouslocations on the path of the conveyance mechanism, for example atsingulation stations, sorting stations, or at other locations, asnecessary or desired. Further, a variety of automated equipment may beused in implementing the automation of the non-linear, unit-levelsortation system using the conveyance receptacles; the use of conveyancereceptacles that may each be associated with individual units of itemsas described herein does not depend on the use of any particularautomated equipment to convey the receptacles and/or to sort the unitscontained therein into respective orders.

Embodiments of the non-linear, unit-level sortation system may enablethe processing of orders within a materials handling facility using onlyone segment, batch and/or process path type, which may reduce theoperating costs for sortation. Additionally, by creating a non-linearrelationship between each item and its associated conveyance receptacleand the sorting mechanism, the total throughput or capacity of thesortation system is modular, and therefore capacity for the sortationsystem is limited only by the space available to induct additionalconveyance receptacles into the non-linear unit-level sortation system.

Thus, embodiments of the non-linear, unit-level sortation system mayprovide improved performance in sorting items into orders in a materialshandling facility when compared to linear sortation systems. In linearsortation systems, capacity/throughput increases typically require theprocurement and operation of additional automated equipment, which isexpensive and space consuming, and typically requires significantadditional labor to operate. In contrast, in the non-linear, unit-levelsortation system, inexpensive conveyance receptacles can be added to theexisting system, with no need to add additional automated equipment, toincrease capacity/throughput. No additional space is required foradditional equipment, and less additional labor, if any, may be requiredto operate at the increased capacity.

The configuration of the transport mechanisms or trays in at least somelinear sorting systems (e.g., tilt trays) may limit the speed at whichthe equipment may be operated, as some items may tend to fly off thetrays at higher speeds. The configuration of the conveyance receptaclesused in embodiments, e.g. trays or totes with relatively high sides, mayhelp to prevent items from falling out of the conveyance mechanism athigher speeds, allowing the conveyance mechanism to be operated athigher speeds if necessary or desired without worrying about itemsfalling off the mechanism.

In addition, a change in the size of items handled in the sortationprocess in linear sortation systems may require expensive modificationsto or replacement of automated equipment. Modifying the linear sortationsystem equipment may result in down-time. In contrast, in thenon-linear, unit-level sortation system, a change in the sizes of itemshandled may typically not result in the need for any change in automatedor down-time for the equipment at all, as the non-linear conveyancereceptacles may handle a larger variety of sizes than the fixed, lineartrays of linear sortation systems, and in addition, different sizes ofconveyance receptacles may be handled by and thus may be added to thenon-linear system without requiring any change of, or even halt of, theautomated equipment. If, for example, items that are too large for thecurrent conveyance receptacles are introduced into the materialshandling facility, then the current conveyance receptacles may bereplaced with or augmented by larger conveyance receptacles. If smalleritems are carried in inventory, then smaller conveyance receptacles maybe used, which has the benefit of allowing increased throughput, as moreconveyance receptacles can be handled by the non-linear system, which islimited only by the space available to induct additional receptaclesinto the system.

In embodiments of the non-linear, unit-level sortation system,non-linear sortation may include a process that may be referred to assingulation. Singulation involves either a human or a machine removingindividual units of items from a collection of mixed items, placing theindividual units of items each into a conveyance receptacle, with onlyone unit per receptacle, and associating the item with the conveyancereceptacle. After a unit of an item is associated with and placed into aconveyance receptacle, the conveyance receptacle may be routed throughthe non-linear, unit-level sortation system to some point or location atwhich the item may be re-grouped with other units of items associatedwith the unit in the receptacle, for example other units of itemsindicated by a customer order or request.

FIG. 1 illustrates a logical representation or view of the operation ofa materials handling facility in which embodiments of the non-linear,unit-level sortation system may be implemented. For example, this Figuremay illustrate an order fulfillment center of a product distributor.Multiple customers 10 may submit orders 20 to the product distributor,where each order 20 specifies one or more items from inventory 30 to beshipped to the customer that submitted the order. To fulfill thecustomer orders 20, the one or more items specified in each order may beretrieved, or picked, from inventory 30 (which may also be referred toas stock storage) in the materials handling facility, as indicated at40. Picked items may be delivered or conveyed, if necessary, to one ormore stations in the materials handling facility for sorting 50 intotheir respective orders, packing 60, and finally shipping 70 to thecustomers 10. In embodiments of the non-linear, flexible sorting system,picked items may be delivered to a singulation station, where individualunits of items are associated with and placed into particular conveyancereceptacles, which are then inducted into a conveyance mechanism. Theconveyance receptacles may then be routed to particular destinations forthe items contained within the receptacles in accordance with therequests (orders) currently being processed, e.g. to sorting stations,under direction of a control system. An exemplary sorting station thatmay be a destination for conveyance receptacles is described below. Apicked, packed and shipped order does not necessarily include all of theitems ordered by the customer; an outgoing shipment to a customer mayinclude only a subset of the ordered items available to ship at one timefrom one inventory-storing location.

A materials handling facility may also include a receiving 80 operationfor receiving shipments of stock from one or more sources (e.g.,vendors) and for placing the received stock into stock storage. Thereceiving 80 operation may also receive and process returned purchasedor rented items or orders from customers. At least some of these itemsare typically returned to inventory 30. The various operations of amaterials handling facility may be located in one building or facility,or alternatively may be spread or subdivided across two or morebuildings or facilities.

FIG. 2 illustrates an example of a physical layout of a materialshandling facility, such as an order fulfillment facility or center, inwhich embodiments of the non-linear, unit-level sortation system may beimplemented. At any one time, one or more agents 42 of the distributormay each be picking items from inventory 30 to fulfill portions or allof one or more requests or orders. This may result in a stream and/orbatches of picked items for multiple incomplete or complete orders,which may then be delivered to an induction point for the non-linear,unit-level sortation system (non-linear sorting mechanism 52). Theinduction point may be referred to as a singulation station, whereindividual units of items are associated with and placed into particularconveyance receptacles, which are then inducted into a conveyancemechanism. The conveyance mechanism, under direction of a controlsystem, may then deliver the conveyance receptacles each including anindividual unit of an item to various order processing stations 55,which may include one or more sorting stations, in the materialshandling facility for processing prior to shipping 70. Portions of anorder may be received from the pickers 42, or from other stations, at aprocessing station 55 at different times, so processing at a station mayhave to wait for one or more items for some orders to be delivered tothe station from picking and/or from another station before completionof processing of the orders at the station.

The picked units of items delivered to a processing station via theconveyance receptacles on the conveyance mechanism may be processed at aprocessing station 55, for example sorted into their respective ordersat a sorting station under direction of the control system. Once theprocessing of items for an order is completed at a station, the itemsmay be delivered to another station for further processing, for exampleto a sorting station to be sorted into orders, or to a packing stationto be packaged for shipping 70.

An order fulfillment center may also include one or more receiving 80operations for receiving shipments 90 of stock from various vendors. Thereceived stock may then be placed into stock storage. The receiving 80operation may also receive and process returned, purchased, or renteditems from customers. The various operations and stations of an orderfulfillment center may be located in one building or facility, oralternatively may be spread or subdivided across two or more buildingsor facilities.

FIG. 3 illustrates an exemplary physical layout of a materials handlingfacility, such as an order fulfillment facility or center, in which anembodiment of the non-linear, unit-level sortation system isimplemented. Requests (e.g., orders) for items from requestors may bedivided among multiple pickers 42, who then pick mixed batches and/or astream of items from inventory storage 30. Picked units of items may beplaced into pick receptacles 102 (e.g., totes or carts) for conveyance.The orders may be subdivided among the pickers 42; therefore, two ormore of the pickers 42 may pick items for one order. Rather thandelivering the picked batches of items or a stream of items directly toa linear automated sorting mechanism, where the individual items areinducted onto fixed carriers or trays on the automated sortingmechanism, the picked batches or a stream of items are delivered to asingulation station 100 or stations (there may be more than onesingulation station 100), for example in pick receptacles 102 (e.g.,totes) each containing one or more units of items, and each possiblycontaining items from two or more orders.

At the singulation station 100, each unit may be pulled individuallyfrom each picked batch (e.g., from a pick receptacle 102) or stream ofitems. Alternatively, all items may be “dumped” into a common receptacle(a bin, basket, shelf, etc.), and individual units may then be pulledfrom the common receptacle. Each pulled unit is then placed into aconveyance receptacle 104 (e.g., a tote or tray), with one and only oneunit placed into each conveyance receptacle 104. Receptacles, as usedherein, may include, but are not limited to, any tote, basket, box,tray, or similar mechanism configured to receive individual units ofitems or batches of units of items in a materials handling facility. Theconveyance receptacle 104 is not fixed to any conveyance mechanism.Again, only one unit of an item is placed into each conveyancereceptacle 104 in various embodiments.

In various embodiments, receptacles, as used herein, may include one ormore virtual receptacles or other designated areas at which items arelocated within the materials handling facility. For instance, in oneembodiment, a receptacle may be a particular portion of a conveyancesystem (e.g., a particular portion of a conveyor belt) on which one ormore units of items may be located. Such virtual receptacles may betracked throughout the materials handling facility by the control systemutilizing various techniques. For instance, the control system maydetermine a location of a virtual receptacle as well as the virtualreceptacle's velocity. The control system may then also determine wherethe virtual receptacle will be in the future based on the location andvelocity. For example, the control system may track a portion of aconveyance system (e.g., a portion of a conveyor belt) by determiningits location from its velocity and a location at which the portion ofconveyance system was located at a particular time. While the example ofa portion of a conveyance system is described above, a virtualreceptacle may in various embodiments be any movable, defined area orvolume configured to receive at least one item within the materialshandling facility.

The pulled unit of an item may be associated with the particularconveyance receptacle 104 it is placed in. In one embodiment, theassociation of a unit of an item with a particular conveyance receptacle104 may be performed by reading, scanning or otherwise entering an itemidentifier associated with the item and a conveyance receptacleidentifier associated with the particular conveyance receptacle 104 intowhich the unit is placed. The item identifier and receptacle identifier106 may be communicated to a control system 190 of the materialshandling facility via wired and/or wireless communications. Eachconveyance receptacle 104 may include a unique conveyance receptacleidentifier that uniquely identifies the particular conveyance receptacle104 in the materials handling facility. The conveyance receptacleidentifier may, for example, be indicated by a bar code, Radio FrequencyIdentifier (RFID) device, or some other scannable or readable mechanism,mark, or tag attached to or integrated with the conveyance receptacle104.

Each unit of each item carried in inventory 30 may include an itemidentifier. A type of item held in inventory 30 may be referred toherein as simply an item. The term item identifier refers to a uniqueidentifier associated with each particular type of item carried ininventory 30 of a distribution system. The term unit may be used torefer to one (unit) of a type of item. Typically, but not necessarily,each unit is tagged or otherwise marked with the item identifier. Forexample, units or collections of items in inventory may be marked ortagged with a bar code, Universal Product Code (UPC), Stock-Keeping Unit(SKU) code, serial number, and/or other designation (includingproprietary designations) that may be used as item identifiers tofacilitate materials handling facility operations, including, but notlimited to, stowing, rebinning, picking, sorting, packing and shipping.These designations, or codes, may identify items by type, and/or mayidentify individual items within a type of item.

Cases, boxes, bundles, or other collections of units of items maysimilarly be marked or tagged with item identifiers. The units of itemsin a collection may all be of the same type of item, for example a caseof 12 units of a particular item, or may be a collection of one or moreunits of each of two or more heterogeneous items. A collection of unitsof item(s) (e.g., a case containing 12 units of an item, or a bundlecontaining one or more units of each of two or more heterogeneous items,such as a boxed or bundled set of three different books) may thus beconsidered or treated as a “unit” in the order fulfillment process. Adesignation, or code, may thus also identify a collection of units ofitem(s) as a “unit” in the order fulfillment process. Thus, embodimentsof the non-linear, unit-level sortation system, in addition to sortingindividual units of items, may also sort collections of units of item(s)designated as units. Therefore, the conveyance receptacles describedherein may receive collections of units of item(s) that are designatedas units as well as individual units of items.

A materials handling facility may include a control system 190 which mayinclude, but is not limited to, one or more computer systems, one ormore data storage devices, one or more wired and/or wireless networks,control system software (programs, modules, drivers, user interfaces,etc.), and one or more hand-held, mobile and/or fixed readers, scannersor scanning devices that may be able to scan, receive, or otherwisedetect the marks or tags (e.g., bar codes, radio frequencyidentification (RFID) tags, etc.) on individual items (units) orcollections of items (e.g., cases) and communicate with a controlstation or stations of the control system to, for example, determine andrecord the item and/or item type of the items. The hand-held, mobileand/or fixed readers, scanners or scanning devices may also be able toscan, receive, or otherwise detect the marks or tags (e.g., bar codes,radio frequency identification (RFID) tags, etc.) attached to orintegrated with the conveyance receptacles. An exemplary computer systemthat may be used in a control system 190 is illustrated in FIG. 13.

At the singulation station 100, a pulled unit of an item may beassociated with a particular conveyance receptacle 104 by reading,scanning, etc. the item identifier associated with the item and theconveyance receptacle identifier associated with the conveyancereceptacle 104 into the control system 190. This may be performedmanually (e.g., by an operator using a hand-held scanner), via anautomated scanning/reading process using fixed scanners/readers, or by acombination of manual and automatic scanning/reading. For example, anoperator at the singulation station 100 may use a hand-held scanner toscan a code off the unit of the item before or during placement of theunit into a “staged” conveyance receptacle 104, while an automatedreader may read (or may have already read) the conveyance receptacleidentifier from the conveyance receptacle 104 that is “staged” for theoperator to place the unit of the item into.

Once a pulled unit of an item is associated with and placed into aparticular conveyance receptacle 104, the conveyance receptacle 104 maybe inducted into a conveyance mechanism 200 (e.g., a conveyor belt,roller system, or other conveyance mechanism) to be conveyed thereby toone or more downstream processing stations for further processing of theunit of the item. In various embodiments, the conveyance mechanism 200may be a conveyance sorter mechanism that includes some method ofdiverting product off a conveyance path under control of a controlsystem. Examples of conveyance sorter mechanisms that may be used asconveyance mechanism 200 may include, but are not limited to, shoesorter mechanisms and pop up sorter mechanisms, such as pop up wheelsorter mechanisms. A pop up wheel sorter includes powered wheels thatrise up out of the conveyor to divert product off the conveyor onto adifferent path or to a location. Other types of conveyance sortermechanism may be used in various embodiments.

The conveyance receptacle 104 may already be on the conveyance mechanism200 when the unit is associated with and placed into the receptacle 104.Alternatively, a conveyance receptacle 104 may be retrieved from aconveyance receptacle storage, stack, or other supply, the unit may beassociated with and placed into the receptacle 104, and the receptacle104 may then be inducted into or placed on the conveyance mechanism 200.The conveyance receptacles 104 are not fixed to the conveyance mechanism200; instead, the receptacles 104 are removable bins, trays, totes, orsimilar devices. The conveyance mechanism 200 may be coupled to andcontrolled by the materials handling facility control system 190 viawired and/or wireless communications. The control system 190 may receiveinput from and send commands to the conveyance mechanism 200 to director control various operations of the conveyance mechanism 200.

The above describes embodiments of a singulation station 100 in which ahuman operator performs at least a portion of the pulling of units ofitems from batches or streams of picked items, scanning/reading theitems and receptacles 104 to associate single units of items toparticular conveyance receptacles 104, and placing the units into theconveyance receptacles 104. In alternative embodiments, some or all ofthe activities described as being performed by a human operator may beperformed by automated mechanisms, which may be coupled to and undercontrol of the materials handling facility control system 190.

Once the conveyance receptacles 104, each containing an individual unitof an item and each associated with the item it contains, are inductedinto the conveyance mechanism 200, the receptacles 104 may be conveyedor routed to any of one or more processing stations, to one or more ofvarious types of sorting mechanisms or processes, to other locations inthe materials handling facility, and so on. In one embodiment, theconveyance mechanism may be directed by the control system 190 as to therouting of each particular conveyance receptacle 104. Since eachconveyance receptacle 104 is associated with the particular item itcontains, the control system 190 may, by tracking the conveyancereceptacle 104 via its unique conveyance receptacle identifier, routethe particular item to an appropriate destination.

The control system 190 may also include or have access to information onthe orders in the order processing stream: for example, which orders arein the process of being fulfilled (i.e., which orders have been assignedto pickers), which orders have been picked, what items in whatquantities are included on each order, and so on. By associatingparticular items associated with particular conveyance receptacles viathe conveyance receptacle identifiers with the orders being processed,the control system 190 may route conveyance receptacles 104 containingunits of items for particular orders to appropriate destinations for theorders, or for portions of the orders (e.g., to a particular one of oneor more sorting stations 152 where particular orders are collected andgrouped to be passed on to packing stations, or to other types ofstations such as gift wrapping stations where pre-packing processing maybe performed on orders or portions of orders, or even on individualunits of items). The routing of conveyance receptacles 104 and theparticular items contained therein may be performed automatically (e.g.,by directing the conveyance mechanism 200 to deliver the conveyancereceptacle 104 to a particular destination) and/or by providingindications to human operators as to the routing or placement ofconveyance receptacles 104 and/or the items contained therein. As anexample of the former, a reader communicatively coupled to the controlsystem 190 may automatically read the conveyance receptacle identifierfrom a receptacle 104 as it passes on the conveyance mechanism 200, andthe control system 190 may then direct the conveyance mechanism 200 toroute the receptacle on a particular one of two or more paths orbranches of the conveyance mechanism 200, for example to a branch thatconveys the receptacle to a particular processing station. As an exampleof the latter, once a receptacle 104 is routed to and arrives at aprocessing station such as a sorting station 152, the conveyancereceptacle identifier may be manually or automatically scanned or readfrom the receptacle 104, and the control system 190 may then activate anindicator on a particular slot, bin, shelf, etc. that is the correctdestination for the item contained in the receptacle 104. The indicatormay be a light, an audio signal, or some other mechanism or combinationof mechanisms capable of conveying audio, visual, and/or otherinformation to a human operator. Alternatively, the indicator may betextual or graphical directions displayed on a monitor of a computer,hand-held device, etc., or printed to paper output.

Once the unit of an item has been pulled from its associated conveyancereceptacle 104 at whatever destination the receptacle is routed to(e.g., a sorting station 152), the item and receptacle 104 may bedisassociated by the control system 190. The empty (and unassociated)conveyance receptacle 104 may then be re-inducted, if necessary, intothe conveyance mechanism 200 to be returned, e.g. to a singulationstation 100 (there may be more than one singulation station 100;therefore, a receptacle 104 is not necessarily returned to the samesingulation station 100 it came from). However, a conveyance receptacle104 is not necessarily immediately re-inducted into the conveyancemechanism 200 when emptied. The conveyance receptacles 104 are not fixedor attached to the conveyance mechanism 200, and there is no necessaryordering of the receptacles 104 on the conveyance mechanism 200;therefore, an emptied conveyance receptacle 104 may be removed and setaside if necessary or desired. When an empty conveyance receptacle 104arrives at a singulation station 100 by the return path of theconveyance mechanism 200, the conveyance receptacle 104 may beassociated with and used to contain and convey a selected unit of anitem from a mixed collection of items, or alternatively may be set asideinto a conveyance receptacle storage area or stack if necessary ordesired. Again, the conveyance receptacles 104 are not fixed to theconveyance mechanism 200, and are not ordered on the conveyancemechanism 200. The conveyance mechanism 200, in other words, isnon-linear.

The above describes a non-linear, unit-level sortation system forsorting mixed and unsorted collections of units of items to variousdestinations according to requests or orders for which the items werepicked. A picking process delivers batches or a continuous stream ofunsorted items for fulfilling requests to one or more singulationstations 100. At the singulation stations 100, individual units of itemsare pulled, associated with particular conveyance receptacles 104, andplaced into the receptacles 104, with one and only one unit perreceptacle 104. The conveyance receptacles 104 are inducted into aconveyance mechanism 200 under the direction of a control system 190that, through various mechanisms, directs the receptacles 104, eachcontaining and associated with a single unit of an item, to particulardestinations. One such destination, in one embodiment, is a sortingstation 152, where the individual items may be manually or automaticallyretrieved from conveyance receptacles 104 and manually or automaticallyplaced into slots or bins corresponding to particular orders. Exemplarysorting stations 152 are illustrated in FIG. 6 and FIGS. 7A and 7B.Empty conveyance receptacles 104 may be returned from the destinationsto the one or more singulation stations 100.

As noted above, the conveyance mechanism 200 is non-linear. Theconveyance receptacles 104 are not fixed to the conveyance mechanism200, and are not ordered on the conveyance mechanism 200. The conveyancemechanism 200 includes at least one conveyance path from the singulationstation(s) 100 to one or more destinations to convey conveyancereceptacles 104 each containing a single unit to the one or moredestinations under direction of the control system 190. The conveyancemechanism 200 also includes at least one return path from at least oneof the destinations to return empty conveyance receptacles to thesingulation station(s) 100. Additional empty conveyance receptacles 104may be inducted into the conveyance mechanism 200, for example toincrease capacity of the non-linear, unit-level sortation system. Emptyconveyance receptacles 104 may be removed from the conveyance mechanism200, for example to reduce capacity of the non-linear, unit-levelsortation system.

Thus, using the non-linear, unit-level sortation system as describedherein, conveyance receptacles 104 may be added to or removed from theconveyance mechanism 200 as necessary or desired, for example todynamically adjust to changes in throughput. This may allow embodimentsto achieve greater velocity and total throughput than, for example,fixed, linear tilt-tray sorting mechanisms, which have a fixed number ofcarriers that go around in a fixed, non-flexible loop. Further, theconveyance receptacles 104 may handle a wider variety of sizes and typesof items than for example a fixed, linear tilt-tray sorting mechanism,with no lower limit on the size of items that can be placed in areceptacle 104, and the upper limit being the volume/dimensions of thereceptacles 104 themselves. Further, different sizes of receptacles 104may be inducted into the conveyance mechanism 200 as necessary ordesired. Larger receptacles 104 may be used if there are a large numberof bigger items being processed in the materials handling facility.Smaller receptacles 104 may be used if the materials handling facilityhandles mostly small items, which would allow the total number ofreceptacles 104 on the conveyance mechanism 200 at one time to beincreased. The maximum number of receptacles 104 that can be on theconveyance mechanism 200 at one time is limited by the size of thereceptacles 104; therefore, the use of smaller receptacles may allowmore receptacles 104 to be on the conveyance mechanism 200 at one time.Further, a mix of different sizes and configurations of receptacles 104may be used on the conveyance mechanism 200 at one time, unlike linear,fixed-receptacle sorting mechanisms that typically have one fixed sizeand configuration of carrier (e.g., tilt tray), which is fixed to thesorting mechanism. Further, if the requirements of the materialshandling facility change, for example if the materials handling facilityincreases or decreases the average size of items carried in inventory,the non-linear, unit-level sortation system may be adapted to handle thechange simply, quickly and inexpensively by replacing some or all of theconveyance receptacles 104 and possibly making some other relativelyinexpensive modifications, with little or no down time, rather thanreplacing or modifying entire linear, fixed-receptacle sortingmechanisms, which can be a very expensive and time-consuming process,which might require significant down time.

FIG. 4 illustrates an exemplary conveyance receptacle according to oneembodiment. Conveyance receptacle 104, may be, but is not limited to, atote, basket, box, tray, or similar mechanism configured to receiveindividual units of items (e.g., a stream of items) or batches of unitsof items in a materials handling facility. Conveyance receptacles 104may come in a variety of sizes, volumes, and configurations. Conveyancereceptacles 104 are not fixed to conveyance mechanism 200, and thusconveyance receptacles 104 can be added to or removed from conveyancemechanism 200. Only one unit of an item is placed into each conveyancereceptacle 104.

Each conveyance receptacle 104 may be associated with a uniqueconveyance receptacle identifier 106 that uniquely identifies theparticular conveyance receptacle 104 in the materials handling facility.The conveyance receptacle identifier 106 may, for example, be a barcode, Radio Frequency Identifier (RFID) device, or some other scannableor readable mark, tag, or device attached to or integrated with theconveyance receptacle 104. FIG. 4 illustrates conveyance receptacle 104as including a receptacle identifier 106 attached to or integrated withthe conveyance receptacle 104 at two locations. However, conveyancereceptacles 104 may have one, two, or more receptacle identifiers 106attached to or integrated with the receptacle. Receptacle identifiers106 may be permanently fixed to conveyance receptacles 104 or,alternatively, may be attachable/removable.

A pulled unit of an item may be associated with a particular conveyancereceptacle 104 it is placed in. In one embodiment, the association of aunit of an item with a particular conveyance receptacle 104 may beperformed by reading, scanning or otherwise entering an item identifierassociated with the item and a conveyance receptacle identifier 106associated with the particular conveyance receptacle 104 into which theunit is placed. The item identifier and receptacle identifier 106 may becommunicated to a control system 190 of the materials handling facilityvia wired and/or wireless communications.

FIG. 5 illustrates operation of an exemplary singulation stationaccording to one embodiment. Requests (e.g., orders) for items fromrequestors may be divided among multiple pickers, who then pick mixedbatches, streams or collections of items from inventory storage. One ormore picked units 108 of one or more items may be placed into pickreceptacles 102 (e.g., totes or carts) for conveyance. The pickedbatches or collections of mixed items may be delivered or conveyed tosingulation station 100, for example in pick receptacles 102 eachcontaining one or more units of one or more items, and each possiblycontaining items from two or more orders. Thus, each pick receptacle maycontain an assortment of various items picked for one or more orders.

Empty conveyance receptacles 104 may be returned to singulation station100 from one or more locations in the materials handling facility (e.g.,from one or more sorting stations 152) on conveyance mechanism 200. Asupply 114 of conveyance receptacles 104 may be kept at or nearsingulation station 100. Arriving receptacles 104 may remain onconveyance mechanism 200 to be used to receive, contain and convey units108 of items or, alternatively, may be removed and placed into supply114.

A unit 108 of an item may be pulled from a pick receptacle 102, forexample by a human operator, at singulation station 100. Alternatively,all batches of items or a stream of items may be “dumped” into a commonreceptacle (a bin, basket, shelf, etc.), and individual units 108 maythen be pulled from the common receptacle. Other methods of inductingitems into singulation station 100 are possible; for example, pulledunits of items may be conveyed to singulation station 100 on a conveyerbelt or roller system. The pulled unit 108 may be associated with aparticular conveyance receptacle 104 and placed into the receptacle 104.One and only one unit 108 is associated with and placed into eachconveyance receptacle 104.

In one embodiment, the association of a unit of an item with aparticular conveyance receptacle 104 may be performed by reading,scanning or otherwise entering an item identifier associated with theitem and a unique conveyance receptacle identifier 106 associated withthe particular conveyance receptacle 104 into which the unit 108 isplaced. In one embodiment, a fixed, mobile, or hand-held reader 194 maybe used to read or scan the item identifier and receptacle identifier106. Associating a pulled unit 108 of an item with a particularconveyance receptacle 104 may be performed manually (e.g., by anoperator using a hand-held scanner), via an automated scanning/readingprocess using fixed scanners/readers, or by a combination of manual andautomatic scanning/reading. For example, an operator at the singulationstation 100 may use a hand-held scanner to scan a code off the unit ofthe item before or during placement of the unit into a “staged”conveyance receptacle 104, while an automated reader may read (or mayhave already read) the conveyance receptacle identifier from theconveyance receptacle 104 that is “staged” for the operator to place theunit of the item into. The read or scanned item identifier andreceptacle identifier 106 may be communicated to a control system 190 ofthe materials handling facility via wired and/or wirelesscommunications.

Once a pulled unit 108 of an item is associated with and placed into aparticular conveyance receptacle 104, the conveyance receptacle 104 maybe inducted into conveyance mechanism 200 (e.g., a conveyor belt, rollersystem, or other conveyance mechanism) to be conveyed thereby to one ormore downstream processing stations for further processing of the unitof the item. In FIG. 5, conveyance mechanism 200 is shown as conveyingreceptacles 104 containing units of items to one or more sortingstations 152, and returning empty receptacles 104 from the sortingstation(s) 152. Exemplary sorting stations 152 to which conveyancereceptacles 104 may be delivered by conveyance mechanism 200 areillustrated in FIG. 6 and FIGS. 7A and 7B. In various embodiments, theconveyance mechanism 200 may be a conveyance sorter mechanism thatincludes some method of diverting product off a conveyance path undercontrol of a control system. Examples of conveyance sorter mechanismsthat may be used as conveyance mechanism 200 may include, but are notlimited to, shoe sorter mechanisms and pop up sorter mechanisms, such aspop up wheel sorter mechanisms. Other embodiments may use othermechanisms as a conveyance mechanism 200.

The conveyance receptacle 104 may already be on the conveyance mechanism200 when the unit 108 is associated with and placed into the receptacle104. Alternatively, a conveyance receptacle 104 may be retrieved from aconveyance receptacle 104 storage, stack, or other supply 114, a unit108 may be associated with and placed into the receptacle 104, and thereceptacle 104 may then be inducted into or placed on the conveyancemechanism 200. Once the conveyance receptacles 104, each containing anindividual unit 108 of an item and each associated with the item itcontains, are inducted into conveyance mechanism 200 at singulationstation 100, the receptacles 104 may be conveyed to any of one or moreprocessing stations, to one or more of various types of sortingmechanisms, to other locations in the materials handling facility, andso on. For example, conveyance receptacles 104 may be conveyed to asorting station 152.

The conveyance mechanism 200 may be coupled to and controlled by thematerials handling facility control system 190 via wired and/or wirelesscommunications. The control system 190 may receive input from and sendcommands to the conveyance mechanism 200 to direct or control variousoperations of the conveyance mechanism 200. The control system 190 may,for example, control conveyance mechanism 200 to direct a particularconveyance receptacle 104 and its associated unit 102 to a particularsorting station 152, as illustrated in FIG. 5.

In one embodiment, a human operator may perform at least a portion ofthe pulling of units 108 of items from batches or streams of pickeditems, scanning/reading the items and receptacles 104 to associatesingle units 108 of items to particular conveyance receptacles 104, andplacing the units into the conveyance receptacles 104 at singulationstation 100. In alternative embodiments, some or all of the activitiesdescribed as being performed by a human operator may be performed byautomated mechanisms, which may be coupled to and under control of thematerials handling facility control system 190.

FIG. 6 illustrates operation of an exemplary sorting station that may beused in embodiments of the non-linear, unit-level sortation system. Oncethe conveyance receptacles 104, each containing an individual unit 108of an item and each associated with the item it contains, are inductedinto the conveyance mechanism 200, at least some of the receptacles 104may be conveyed to sorting station 152. In one embodiment, theconveyance mechanism may be directed by the control system 190 as to thedisposition of each particular conveyance receptacle 104. Since eachconveyance receptacle 104 is associated with the particular item itcontains, the control system 190 may, by tracking a particularconveyance receptacle 104 via its unique conveyance receptacleidentifier 106, direct the conveyance mechanism to route the particularconveyance receptacle 104 and its associated unit 108 of the item tosorting station 152 from an originating singulation station 100.

To route a particular conveyance receptacle 104 and its associated unit108 of an item to a particular destination, the control system 190 mayalso include or have access to information on the orders in the orderprocessing stream: which orders are in the process of being fulfilled(i.e., which orders have been assigned to pickers and/or which ordersare currently assigned to pickers), which orders have been picked, whatitems in what quantities are included on each order, and so on. Thecontrol system may associate a particular conveyance receptacle 104including a unit 108 of a particular item with a particular ordercurrently being processed in the order fulfillment process, and mayroute the conveyance receptacle 104 to an appropriate destination forthe order (e.g., to sorting station 152 of FIG. 6). The routing ofconveyance receptacles 104 may be performed automatically (e.g., bycontrol system 190 directing the conveyance mechanism 200 to deliver aconveyance receptacle 104 to a particular destination). As an example, areader communicatively coupled to the control system 190 mayautomatically read the conveyance receptacle identifier from areceptacle 104 as it passes on the conveyance mechanism 200, and thecontrol system 190 may then direct the conveyance mechanism 200 to routethe receptacle on a particular one of two or more paths or branches ofthe conveyance mechanism 200, for example to a path that conveys thereceptacle to sorting station 152.

Control system 190 may also provide audible, visual, or otherindications to human operators as to the routing or placement ofconveyance receptacles 104 and/or the units 108 of items containedtherein. For example, once a particular conveyance receptacle 104arrives at sorting station 152, the conveyance receptacle identifier 106may be manually or automatically scanned or read from the receptacle 104and communicated to control system 190. In one embodiment, a fixed,mobile, or hand-held reader 196 may be used to read or scan theconveyance receptacle identifier 106. After the conveyance receptacleidentifier 106 is read, the control system 190 may activate an indicator158 associated with a particular order slot 156 of an order sorting bin154 located at the sorting station 152 that assigned to an order that isassociated with receptacle 104 and thus with the unit 108 of an itemcontained therein. The indicator 158 may be a light, an audio signal, orsome other mechanism or combination of mechanisms capable of conveyingaudible, visual, and/or other information to a human operator. As analternative, or in addition, to indicators 158 physically locatedproximate to slots 156 on sorting bin 154, textual and/or graphical itemplacement directions may be displayed on a monitor of a computer,hand-held device, etc., or printed to paper output for operator(s) atsorting station 152.

There may be one or more order processing stations 155 associated withsorting station 152. In this example, an order processing station 155 islocated on the other side of order sorting bin 154. Order processingstation 155 may, for example, be a packing station at which one or moreunits 108 of items for an order are processed, packed, and labeled forshipping to the customer. The order slots 156 may be pass-through slotsinto one side of which units 108 of items may be placed, and out ofwhich individual or collections of units 108 of items may be removed forprocessing. In one embodiment, units 108 of items may be removed fromconveyance receptacles 104 and placed into a particular slot (e.g., item108 is illustrated as being placed into slot (3, 2)) as indicated by thecontrol system 190, for example by the control system 190 activating anindicator 158 associated with the slot 156 into which the unit 108 is tobe placed to indicate to the operator that the unit 108 from the currentreceptacle 104 is to be placed into that slot 156. Sorting bin 154 mayalso include indicators associated with the slots 156 on the orderprocessing station 155 side which control system 190 may activate toindicate to operators at the order processing station 155 that aparticular slot 156 is ready to be processed (e.g., that all units 108of all items for an order have been placed into that slot). In thisexample, control system has indicated to operator(s) at order processingstation 155 that an order 160 in slot (2, 1) has been completed. Anoperator may then pull the order 160 from the slot 156 for furtherprocessing. For example, the operator may be prompted by control system190 (e.g., via a an indicator such as a light or display) to forwardorder 160 to a subsequent processing station.

A sorting process using a singulation station 100, conveyancereceptacles 104 each including one unit 108 of an item, and a conveyancemechanism 200, under direction of control system 190, may free operatorsat sorting stations 152 from having to scan each individual item duringsorting. In one embodiment, the conveyance receptacle identifier 106 maybe automatically read by a reader 196 as the receptacle 104 approachesor enters the location of sorting station 152 at which the operatorremoves units 108 from receptacles. The operator may thus simply removethe unit 108, look to see which indicator 156 is currently activated bycontrol system 190, and place the unit 108 into the associated slot 154.

Once the unit 108 of an item has been pulled from its associatedconveyance receptacle 104 at sorting station 152, the item andreceptacle 104 may be disassociated in the control system 190. Thecontrol system 190 may determine via the processing at sorting station152, or alternatively may be informed via operator interaction with thecontrol system 190, that the conveyance receptacle 104 is now empty. Theempty (and unassociated) conveyance receptacle 104 may then bere-inducted, if necessary or desired, into the conveyance mechanism 200to be returned, for example, to a singulation station 100. There may bemore than one singulation station 100 in a materials handling facility;therefore, a receptacle 104 is not necessarily returned to the samesingulation station 100 that it originated from. A conveyance receptacle104 is not necessarily immediately re-inducted into the conveyancemechanism 200 when emptied. The conveyance receptacles 104 are not fixedor attached to the conveyance mechanism 200, and there is no necessaryordering of the receptacles 104 on the conveyance mechanism 200;therefore, an emptied conveyance receptacle 104 may be removed and setaside if necessary or desired.

FIGS. 7A and 7B illustrate a side view and a top view, respectively, ofan exemplary sorting station and associated order processing stationsaccording to one embodiment. In this example, a sorting station 152includes two order sorting bins 154A and 154B. Order processing station155A is located on the other side of order sorting bin 154A, and orderprocessing station 155B is located on the other side of order sortingbin 154B. Conveyance mechanism 200 may induct a particular conveyancereceptacle 104 to the sorting station 152 as the current or activereceptacle 104A. In one embodiment, a reader 196 (see FIG. 7B) may readthe receptacle identifier 106 from the receptacle 104A as or prior tothe induction of the receptacle 104A to the sorting station 152 as theactive receptacle 104A. Control system 190 may then activate anindicator 158 on a particular order slot 156 of one or the other of theorder sorting bins 154 to indicate to the operator that the unit of theitem in the active receptacle 104A is to be placed into the associatedorder slot 156. After the item is pulled from the active receptacle 104Aand placed in the slot 156, the indicator may deactivate, and thecontrol system 190 may disassociate the item from the active receptacle104A to indicate the receptacle 104A is empty. The active receptacle104A may then be conveyed onto a return path of the conveyance mechanism200, and the next conveyance receptacle 104B on the conveyance mechanism200 may be inducted as the active receptacle.

Sorting bins 154 may also include indicators associated with the slots156 on the order processing station 155 side which control system 190may activate to indicate to operators at the order processing stations155 that a particular slot 156 is ready to be processed (e.g., that allunits 108 of all items for an order have been placed into that slot).Once control system has indicated to operator(s) at order processingstations 155 that an order in a slot 156 has been completed, an operatormay then pull the order from the slot 156 for further processing. Inembodiments, sorting bins 154 may have different configurations. Forexample, sorting bins 154A and 154B are illustrated with different sizeslots 156 in FIG. 7B.

In one embodiment, one or more other receptacles (e.g., transfer tote162) may be located at or near sorting station 152. Control system 190,after reading the receptacle identifier 106 of active receptacle 104,may activate an indication (e.g., a light) that indicates to theoperator that the item in the active receptacle 104 is to be placedinto, e.g., the transfer tote 162. When the transfer tote 162 is full,the operator may then convey, or induct the transfer tote 162 intoanother conveyance mechanism, to deliver the transfer tote 162 toanother processing station or destination in the materials handlingfacility. Transfer totes 162 may be marked with transfer toteidentifiers similar to the conveyance receptacle identifiers, and thusmay be tracked by control system 190. After a transfer tote 162 isconveyed from the sorting station 152, a new transfer tote 162 may beplaced at the sorting station 152.

Processed (e.g., packed) orders and/or other receptacles such astransfer totes 162 may be conveyed from order processing stations 155and/or sorting station 152 via processed order/transfer tote conveyance210, as illustrated in FIG. 7B. Processed order/transfer tote conveyance210 may, for example, be a conveyor belt mechanism, roller system,manual or motorized carts, or some other mechanism.

FIG. 6 and FIGS. 7A and 7B illustrate and describe embodiments of asorting station 152 in which a human operator performs at least aportion of the pulling of units 108 from conveyance receptacles 108 andplacing the units into slots 156 of an order sorting bin 156. Inalternative embodiments, some or all of the activities described asbeing performed by a human operator at a sorting station 152 may beperformed by one or more automated mechanisms, which may be coupled toand under direction and control of the materials handling facilitycontrol system 190.

FIGS. 8A through 8E illustrate exemplary configurations for ordersorting bins that may be used in various embodiments. In variousembodiments, sorting bins 154 may have different configurations, andsorting bins with different configurations may be used together in animplementation of the non-linear, unit-level sortation mechanism thatuses sorting stations 152 similar to those illustrated in FIG. 6 andFIGS. 7A and 7B. Sorting bins may have different size slots toaccommodate larger or smaller orders and/or larger or smaller items.FIG. 8A illustrates an order sorting bin with 112 6″×6″ slots. FIG. 8Billustrates an order sorting bin with 32 12″×12″ slots. FIG. 8Cillustrates an order sorting bin with 24 12″×18″ slots. FIG. 8Dillustrates an order sorting bin with 24 16″×16″ slots. FIG. 8Eillustrates an exemplary hybrid order sorting bin that includes six16″×16″ slots, eight 12″×18″ slots, eight 12″×12″ slots, and 22 9″×9″slots. While the example of FIG. 8E illustrates a sorting bin havingslots that varying in size with respect to rows, in various embodimentssuch a hybrid sorting bin may include slots that vary in size withrespect to columns.

FIG. 9 is a flowchart illustrating a method of operation in anon-linear, unit-level sortation system according to one embodiment.This flowchart illustrates how the various components described herein,e.g. one or more singulation stations, a plurality of free-floatingconveyance receptacles each identified by a unique receptacleidentifier, a conveyance mechanism, one or more sorting stations, and acontrol system, may be integrated to form a non-linear, unit-levelsortation system for handling the sortation of mixed batches or streamsof items picked to fulfill orders the materials handling facility. Themethod as illustrated in FIG. 9 may be performed as a continuous ornear-continuous process by the non-linear, unit-level sortation systemin the materials handling facility to sort a continuous ornear-continuous incoming stream of mixed items picked to fulfill ordersinto their respective orders.

Elements 201 through 206 may be performed at a singulation station, suchas singulation station 100 illustrated in FIGS. 3 and 5. Element 208 maybe performed by a conveyance mechanism, such as conveyance mechanism 200illustrated in FIGS. 3, 5, 6, 7A and 7B, which may be controlled by acontrol system 190 as illustrated in those Figures. An exemplarycomputer system that may implement software components and functionalityof control system 190 is illustrated in FIG. 13. Elements 210 through216 may be performed at a sorting station, such as sorting station 152illustrated in FIGS. 3, 6, 7A and 7B.

A pick process in the materials handling facility may generate batchesor a stream of picked units of heterogeneous items that are mixedtogether in one or more collections (e.g., in pick receptacles). Thecollections of items may be delivered to one of one or more singulationstations in the materials handling facility. As indicated at 201, at asingulation station, single units may be selected from the collection ofitems that includes units of heterogeneous items picked from theinventory storage of the materials handling facility to fulfill aplurality of orders. The selection of single units from the collectionmay be performed manually or automatically in various embodiments. Asindicated at 202, an item identifier of a selected unit may beassociated with a receptacle identifier of an empty conveyancereceptacle. To associate the item identifier with the conveyancereceptacle, the item identifier may be manually or automatically readfrom the selected unit, e.g. by a fixed or hand-held scanner or reader,and the receptacle identifier may be manually or automatically read fromthe conveyance receptacle into which the selected unit is to be placed,e.g. by a fixed or hand-held scanner or reader. In one embodiment, thereceptacle identifier may be indicated by a bar code attached to orintegrated with the conveyance receptacle, and to read the receptacleidentifier from the conveyance receptacle, the bar code may beelectronically scanned from the conveyance receptacle, e.g. by a fixedor hand-held scanner. In one embodiment, the receptacle identifier maybe indicated by a Radio Frequency Identifier (RFID) tag attached to orintegrated with the conveyance receptacle, and, to read the receptacleidentifier from the conveyance receptacle, the RFID tag may be read fromthe conveyance receptacle, e.g. by a fixed or hand-held RFID reader. Theitem identifier and receptacle identifier may be communicated to acontrol system, at which the two identifiers may be associated. Thecontrol system may also include information on orders currently beingprocessed, and thus may associate the conveyance receptacle and the itemcontained in the conveyance receptacle with a particular order thatindicates at least one unit of the item.

As indicated at 204, the selected unit may be placed into the associatedconveyance receptacle and, as indicated at 206, the conveyancereceptacle containing the selected unit may be inducted into theconveyance mechanism to be conveyed thereby to a destination in thematerials handling facility, such as a sorting station. The emptyconveyance receptacle may have been retrieved from a receptacle supplyat or near the singulation station prior to induction, or alternativelymay have already been on the conveyance mechanism, e.g. the conveyancereceptacle may be an empty receptacle returned via the conveyancemechanism from a sorting station. The conveyance receptacles are notfixed to the conveyance mechanism, and therefore can be placed on orremoved from the conveyance mechanism as necessary or desired.

As indicated at 208, the conveyance mechanism may convey the conveyancereceptacle to a particular one of one or more sorting stations in thematerials handling facility that is the destination for an order thatspecifies at least one unit of the item contained in and associated withthe conveyance receptacle. A control system may direct the conveyancemechanism to route the conveyance receptacle to the correct destination,e.g. a sorting station at which an order specifying at least one unit ofthe item contained in the conveyance receptacle is to be collected forprocessing.

As indicated at 210, the conveyance receptacle containing the unit ofthe particular item may be received at the sorting station. At thesorting station, the unit of the particular item may be manually orautomatically removed from the conveyance receptacle, as indicated at212. The unit may then be manually or automatically placed into aparticular location at the sorting station associated with an order thatindicates at least one unit of the particular item associated with theconveyance receptacle, as indicated at 214. In one embodiment, theparticular location may be a particular slot of an order sorting bin,such as one of the exemplary order sorting bins 154 illustrated in FIGS.6 through 8E.

In one embodiment, to place the unit into a particular location at thesorting station, the receptacle identifier may be manually orautomatically read from the conveyance receptacle at or near the sortingstation, and an indicator associated with the particular location may beautomatically activated in response to reading the receptacle identifierto indicate to an operator that the unit of the particular itemassociated with the conveyance receptacle is to be placed into thatparticular location.

As indicated at 216, the empty conveyance receptacle may be, but is notnecessarily inducted into a return path of the conveyance mechanism toreturn the conveyance receptacle to one of one or more singulationstations. The control system may direct the conveyance mechanism toreturn the empty conveyance receptacle to a particular one of one ormore singulation stations, or alternatively may direct the conveyancesystem to route the empty conveyance receptacle to some otherdestination. At a singulation station, the returned empty conveyancereceptacle may be associated with another item, receive a unit of theitem selected from a collection, and then be conveyed by the conveyancemechanism back to the singulation station or to another destinationunder direction of the control system. Alternatively, empty conveyancereceptacles may be removed from the conveyance mechanism at the sortingstation(s), singulation station(s), or at other locations along ordestinations of the conveyance mechanism.

Managing the Allocation of Items to Processing Stations

As described above, the order fulfillment center may include multipleorder processing stations, which may include multiple sorting stations(e.g., sorting stations 152) for sorting items into completed orders.Additionally, a conveyance mechanism, under direction of a controlsystem, may deliver conveyance receptacles (each including an individualunit of an item) to such order processing stations. For instance, asillustrated in FIG. 3, conveyance mechanism 200 delivers ones ofconveyance receptacles 104 to both sorting station 152A and sortingstation 152B. To prevent inefficiencies and undesirable situations, suchas the gridlock of conveyance receptacles on conveyance mechanism 200,the flexible, non-linear, unit-level sortation system may include anitem allocation component configured to dynamically allocate items(and/or the conveyance receptacles that carry such items) to varioussorting stations within the order fulfillment center. FIG. 10illustrates a portion of the order fulfillment center described hereinas well as one such item allocation component, illustrated as itemallocation component 300. Item allocation component 300 may in someembodiments be configured as a component of control system 190 (which,as described above, is configured to control conveyance mechanism 200).In other embodiments, item allocation component 300 may be configured asa separate component or system configured to provide item allocationinformation to control system 190, which may use such information todirect the flow of items (and/or the conveyance receptacles that carrysuch items) to various sorting stations. In various embodiments, thefunctionality of item allocation component 300 may be implemented asinstructions stored on and executable by a computer system, such ascomputer system 900 described in more detail below.

In various embodiments, conveyance mechanism 200 (e.g., a conveyor belt,roller system, or other conveyance mechanism) may include a conveyanceloop configured to circulate items throughout the order fulfillmentcenter. Such conveyance loop may include a variety of ingress and egresspoints, from which conveyance receptacles (and the items carried withinthem) may enter and exit the conveyance loop, respectively. One exampleof an ingress point on the conveyance loop may include an inductionpoint, such as the singulation station described above. An egress pointon the conveyance loop may be utilized to send items to various orderprocessing stations or to remove items that have been circulating on theloop for a specified amount of time. Note that while items withinconveyance receptacles may be “circulated” throughout the orderfulfillment center, such description is not intended to limit the formor shape of the conveyance mechanism to a circle or any other form orshape. In various embodiments, the conveyance mechanism may take onvarious forms including both regular and irregular or freeform shapes.

Note that FIG. 10 illustrates only a portion of the conveyance loop,which is denoted as conveyance loop subsection 310. Conveyance mechanism200 may direct the flow of conveyance receptacles to various sortingstations (and/or any other order processing stations, as describedabove) via one or more chutes, takeaway conveyors, or other conveyancemechanisms, which are referred to herein as “item buffers” andillustrated as item buffers 320A-320D. While such conveyance mechanismsare referred to herein as item buffers, other configurations (such asdesignating only a portion of a chute, takeaway conveyor, or otherconveyance mechanism as an item buffer) may be employed while remainingwithin the spirit and scope of various embodiments. Additionally, insome embodiments, there may be one or more intermediate conveyancemechanisms between the conveyance loop and such item buffers. Note thatin the illustrated embodiment, the capacity of the item buffers isapproximately 3-4 conveyance receptacles. However, the illustratedembodiment is not necessarily drawn to scale. In one exemplaryembodiment, the capacity of the item buffers is 20 conveyancereceptacles. However, in various other embodiments, the capacity of theitem buffers may be any number of conveyance receptacles (or items).

The process of directing an item from the conveyance loop to an itembuffer may be referred to herein as “diverting” an item. With respect toitem diversion, items may be in a variety of states including but notlimited to “pending divert” (which refers to items currently on theconveyance loop), “undergoing divert” (which refers to items currentlybeing diverted from the conveyance loop to an item buffer), and“diverted” (which refers to items that are currently within the itembuffer). The following description largely describes the diversion ofitems to item buffers of sorting stations; however, in various cases“diverting” an item may generally refer to directing an item from acurrent path on the conveyance mechanism to a next path on or off theconveyance mechanism.

FIG. 10 illustrates a variety of active conveyance receptacles denotedas active receptacles 104A-104J. In the illustrated embodiment, activereceptacles 104A, 104B, 104C, 104D, 104E, 104F, 104G and 104H have beendiverted and are awaiting sortation in respective ones of item buffers320A-D. Also in the illustrated embodiment, active receptacle 1041 isundergoing diversion from the conveyance loop to item buffer 320A whileactive receptacles 104J-104K remain on the conveyance loop. Note thatthe portion of the order fulfillment center illustrated in FIG. 10represents the state of such portion at a given instant in time. Otherrepresentations, reflecting other instances in time, will be apparentfrom this disclosure. For instance, at some time subsequent to theillustrated instance, ones of active receptacles 104A, 104B, 104C, 104D,104E, 104F, 104G and 104H may be removed from item buffers 320A-320D andprocessed at sorting stations 152A-152D. Likewise, active receptacle1041 may be fully transitioned from the undergoing divert state to thediverted state. Additionally, active receptacles 104J and 104K mayeventually be diverted to an item buffer or removed from the conveyanceloop. Further, subsequent conveyance receptacles may arrive from theinduction point or some other previous portion of the conveyance loop.In general, the illustrated portion of the order fulfillment centerdepicts only a single instance of a dynamic and frequently changingenvironment within the order fulfillment center.

Under the direction of control system 190 and/or item allocationcomponent 300, various mechanical elements (such as divert mechanisms315) may be utilized by the flexible, non-linear, unit-level sortationsystem to divert conveyance receptacles to various locations within theorder fulfillment facility. In the illustrated embodiment, divertmechanisms 315 are illustrated as shoes of a sliding shoe sorter.However, in other embodiments, other mechanical elements may be used todivert items to item buffers or other locations within the orderfulfillment facility. Such mechanized elements may include but are notlimited to narrow belt sorters, cross belt sorters, angled roller topsorters, high speed pushers, and other sortation devices. In variousembodiments, the diversion and conveyance of conveyance receptacles(and/or items carried by such receptacles) are not limited to anyparticular conveyance elements.

In various embodiments, control system 190 may be tasked with managingsuch dynamic and frequently changing environment by controlling the flowof conveyance receptacles throughout the order fulfillment center.Furthermore, the allocation or assignment of conveyance receptacles(and/or the items carried by them) to various sorting stations 152A-152Dor some other sorting station or order processing station may becontrolled or specified by item allocation component 300. Note thatembodiments are not limited to only four order processing stations(e.g., sorting stations 152A-152D). Instead, any number of processingstations may be utilized in various embodiments. In some embodiments, ashistorical or projected ordering activity fluctuates, the flexible,non-linear, unit-level sortation system may be scaled by adding orderprocessing stations to or removing order processing stations from theflexible, non-linear, unit-level sortation system. As described above,item allocation component 300 may assign or direct conveyancereceptacles to various locations within the order fulfillment center,some of which may include item buffers 320A-320D. Note that embodimentsare not limited to the four illustrated item buffers. In general, anynumber of item buffers may be deployed within the order fulfillmentcenter.

As described herein, item allocation component 300 may control the flowof conveyance receptacles within the order fulfillment facility. Sinceeach conveyance receptacle may carry one unit of an item, it will bereadily apparent that item allocation component 300 is also configuredto control the flow of items within the order fulfillment facility. Inthis disclosure, item allocation component 300 may be referred to asdirecting a conveyance receptacle or directing an item (within suchreceptacle) to various locations within the order fulfillment center. Itwill be understand that, due to the singulation of items at induction(e.g., the association of one unit of an item with a particularconveyance receptacle as described above regarding FIGS. 4 and 5),directing the flow of a particular conveyance receptacle within theorder fulfillment center may also be considered as directing the flow ofa particular unit of an item within the order fulfillment center. Insome cases, such as when conveyance receptacles are active (e.g.,carrying a unit of an item), the reference of the item allocationcomponent as directing the flow of conveyance receptacles and thereference of the item allocation component as directing the flow ofitems may be used interchangeably.

As described in more detail below, the manner in which the itemallocation component allocates or assigns conveyance receptacles tovarious item buffers (and/or to the sortation stations coupled to suchitem buffers) may prevent the gridlock of items on the conveyance loop.Gridlock occurs when the conveyance loop is “full” of conveyancereceptacles. In other words, gridlock may include situations where theconveyance loop can no longer receive additional inducted items withoutadversely affecting the performance of the conveyance mechanism.Gridlock can occur for a variety of reasons. In one example, gridlockmay occur when the overall rate of offload (e.g., the rate at whichitems are diverted to item buffers) does not meet or exceed the overallrate of induction (e.g., the rate at which items are inducted into thesystem). In some cases, the conveyance mechanism may sustain shortperiods of time in which the rate of induction exceeds the rate ofoffload. However, generally speaking, if the rate of induction exceedsthe rate of offload for an extended period of time, the conveyancemechanism may experience item gridlock at some point.

One particular example of item gridlock can occur when a previouslyunutilized sorting station becomes active. A sorting station may bepreviously unutilized for a variety of reasons. For example, the sortingstation may be newly constructed and activated for the first time. Inanother example, the sorting station may simply be unused because of lowrequisite item throughput (e.g., due to lulls in the number of completedorders). In another example, a sorting station may be unutilized beforethe first shift of a given day (e.g., before agents logon to the sortingstation to begin processing items). In any case, when a sorting stationis activated (or “enabled”) from an inactive state, the sorting stationis typically (although not necessarily) void of items. For instance,order sorting bins (see e.g., FIGS. 8A-8E) may be completely or nearlyempty. If a control system primarily makes decisions based on theutilization of the order sorting bins (e.g., how many items are storedin or assigned to a given order sorting bin), such control system mayinadvertently gridlock the conveyance loop. More specifically, there istypically a delay between the time that items are assigned to a sortingstation and the time that items actually arrive at such sorting station;such delay may be caused by the items' travel time on the conveyancemechanism to the sorting station. Gridlock can occur if a control systemover allocates items by primarily basing allocation decisions on theutilization of an order sorting bin of a sorting station.

Consider the following example. An order sorting bin of a sortingstation has 40 free slots. A control system then allocates 40 inducteditems (each of disparate orders) to such sorting station. The 40 itemsthen travel on a conveyance mechanism for a given time period. If a newcollection of 35 items (each of disparate orders) is inducted into theconveyance system and the control system allocates such items while theprevious 40 items are en route to the aforementioned sorting station,the control system might allocate the 35 newly inducted items to thesame sorting station. For instance, if such control system onlyevaluates the utilization of the order sorting bin at such station, thecontrol system might determine that the station has capacity for 40additional items (e.g., since in this example the control system doesnot take into consideration the original 40 items en route to thesorting station). The end result in this example is the allocation of 75items (each of disparate orders) to a sorting station that currently hascapacity for 40 orders. If the item buffer associated with the sortingstation cannot fully absorb the additional 35 items, the remaining itemswill be circulated on the conveyance loop. It is this circulation thatis frequently the culprit of item gridlock on the conveyance loop.Granted, in some cases, a conveyance loop may be able to sustain a givennumber of circulated items for a short period of time without becominggridlocked. However, in general, if the above situation is replicated ona large enough scale (as is often the case), the conveyance loop willeventually become gridlocked.

Item allocation component 300 described herein (whether alone or as acomponent of control system 190) may prevent item gridlock through themanner in which it allocates and/or directs items (or conveyancereceptacles) to sorting stations. In various embodiments, for a givenconveyance receptacle inducted into the conveyance mechanism, the itemallocation component 300 may allocate and/or direct the conveyancereceptacle to the sorting station that is best equipped to process theinducted item as determined based on one or more “allocation criteria,”examples of which are described in more detail below.

In various embodiments, for a given conveyance receptacle inducted intothe conveyance mechanism, the item allocation component 300 may allocateand/or direct the conveyance receptacle to the sorting station that isbest equipped to process the inducted item as determined based onallocation criteria including whether or not a given sorting station isenabled. Sorting stations may reside in an enabled or disabled state fora variety of reasons. The item allocation component described herein maybe configured to determine whether a given sorting station is enabled ordisabled. Typically, a sorting station is enabled if it is ready for anagent to login or if it already has at least one agent logged in. Asorting station may be disabled for a variety of reasons including butnot limited to repairs, routine maintenance and equipment upgrades. Inother cases, some sorting stations may be disabled because order demanddoes not warrant the use of all sorting stations. In some cases, theamount of available labor or agents capable of operating a sortingstation may be less than the required amount of labor to operate allsorting stations in the order fulfillment center. In such cases, anumber of sorting stations may be left disabled until more labor becomesavailable.

In various embodiments, for a given conveyance receptacle inducted intothe conveyance mechanism, the item allocation component 300 may allocateand/or direct the conveyance receptacle to the sorting station that isbest equipped to process the inducted item as determined based onallocation criteria including the available slot categorizations amongsteach of the sorting stations and their associated order sorting bins. Agiven slot categorization may represent actual slot dimensions (e.g.,6″×6″, 12″×12″, 12″×18″, etc.) or relative slot dimensions (e.g., small,medium, large, etc.) or some other categorization of the slot (e.g., acategorization based on volume of the slot). In some embodiments,sorting stations may include order sorting bins with uniform slotcategorizations (see e.g., FIGS. 8A-8D) or hybrid (e.g., mixed) slotcategorizations (see e.g., FIG. 8E). Item allocation component 300 maybe configured to, for a given sorting station, determine the varioustypes slot categorizations (e.g., small, medium, large) at a particularsorting station as well as the quantity of each (e.g., 30 small, 20medium, 10 large) slot having such slot categorizations.

Additionally, the item allocation component may be configured todetermine, for a given item of an order, the best-fit slotcategorization (which may also be referred to as the best-fit slot size)for such order. For instance, in one embodiment, the best-fit slotcategorization may be the smallest slot categorization that is able tohold all items of the order. In various embodiments, the item allocationcomponent described herein may be configured to determine the volumetricrequirements of a given order (with or without packing materials such asdimensional padding, protective foam, air-filled packaging, etc.) anddetermine a slot categorization capable of holding an order of itemshaving such volumetric requirements. In various embodiments, in responseto determining the best-fit slot categorization, the item allocationcomponent may determine one or more sorting stations that have availablesorting slots (e.g., sorting slots which do not already contain an item)and assign a given item or conveyance receptacle to one of such sortingstations.

In one embodiment, the item allocation component may be configured todetermine the volumetric requirements of a given order and/or a slotcategorization capable of holding an order having such volumetricrequirements by requesting such information from a container recommendercomponent. Embodiments of a flexible, non-linear, unit-level sortationsystem include a container recommender configured to instruct orrecommend the selection, from among available containers, of a containerin which to place one or more items, or a portal or path through whichto convey the items, during the receiving, storing in inventory,picking, sorting, packing or shipping operations described above. Forexample, the system may be configured to recommend various boxes orother containers suitable for shipping one or more items or for storingor conveying one or more items in the materials handling facility,dependent on item dimension values and/or weight values currentlyassociated with the items. In one embodiment, the system may recommend aparticular box type and/or size suitable for shipping a group of itemsassociated with a customer order based on item dimension values and/orweights provided by the vendor of each of the items in the group and thedimensions and weight limitations of the boxes available for shipping.In other embodiments, the system may recommend a particular box typeand/or size suitable for shipping a group of items dependent on itemdimension values and/or weights measured in the facility or learned bythe packaging information system through an automated process ofsuccessive approximation. In some embodiments, the selection ofcontainers that are neither too small nor larger than they need to bemay result in more efficient use of space in the facility for storageand other operations, and may also reduce costs associated with floorspace, packing materials, or transportation (e.g., shipping). In someembodiments, the container recommender may be used to estimatecorresponding dimensions of a container suitable for storing,transporting, or shipping the items that is space-efficient and/or costeffective. In various embodiments, the techniques employed by thecontainer recommender may also be employed to determine an appropriateslot categorization for a given order of items (with or with outpackaging materials). While in some embodiments the item allocationcomponent may, for a given order, request and receive an indication ofthe best slot categorization for such order from the containerrecommender, in other embodiments the item allocation component may beconfigured to independently determine such best slot categorizationutilizing techniques similar to or the same as those employed by the boxrecommender.

In various embodiments, for a given conveyance receptacle inducted intothe conveyance mechanism, the item allocation component 300 may allocateand/or direct the conveyance receptacle to the sorting station that isbest equipped to process the inducted item as determined based onallocation criteria including the available labor at a given sortingstation. Labor may include human operators and/or mechanized orautomated agents. Generally, the more available labor at a givenstation, the faster it can perform work (e.g., sort items). Accordingly,the item allocation component describe herein may in some cases allocateor direct items to sorting stations having measures of available laborthat are higher than measures of available labor at other sortingstations.

In various embodiments, for a given conveyance receptacle inducted intothe conveyance mechanism, the item allocation component 300 may allocateand/or direct the conveyance receptacle to the sorting station that isbest equipped to process the inducted item as determined based onallocation criteria including the quantity of conveyance receptacles ata given sorting station and/or the quantity of conveyance receptaclesdestined for (e.g., en route or waiting in an item buffer) such sortingstation. Items at a given sorting station may include items that havebeen removed (e.g., decoupled) from a conveyance receptacle, such asillustrated by unit 106 of FIG. 6. Items at the given sorting stationmay also include items currently being handled by an agent or operator(e.g., such as items in the process of being sorted into a slot of anorder sorting bin). Additionally, items at the given sorting station mayalso include items stored in slots of an order sorting bin. Itemsdestined for the sorting station may include items that have beeninducted but have not yet been decoupled removed (e.g., decoupled) fromtheir respective sorting bin at the sorting station. Such items mayinclude items transported by the conveyance mechanism (e.g., items onthe conveyance loop) that have not yet reached their assigned sortingstation. Such items may also include items waiting in the sortingstation's item buffer.

In various embodiments, for a given conveyance receptacle inducted intothe conveyance mechanism, the item allocation component 300 may allocateand/or direct the conveyance receptacle to the sorting station that isbest equipped to process the inducted item as determined based onallocation criteria including the number of available slots at a givensorting station, the number of shipments or orders assigned to a givensorting station (whether items of such shipments are at the sortingstation or en route to the sorting station), and/or the number ofoccupied slots at a given sorting station. Regarding the number ofavailable slots at a given sorting station, in some cases such value maybe determined by subtracting the number of slots that include at leastone item as well as the number of unusable slots (e.g., such as slotsthat are fully or partially blocked by other equipment) from the totalnumber of slots at a given sorting station. In some cases, for a givenconveyance receptacle inducted into the conveyance mechanism, the itemallocation component 300 may allocate and/or direct the conveyancereceptacle to the sorting station that is best equipped to process theinducted item as determined based on allocation criteria including thenumber of incomplete and/or the number of complete orders at a givensorting station. A complete order may include a sorted group of itemscontaining all items of the respective order (see e.g., completed order160 of FIG. 6). An incomplete order may include one or more items thatare at least one item short of being a group including all the items ofthe respective order.

In some embodiments, the determination of which sorting station toallocate or direct a given item may only be performed for the firstinducted item of an order. For instance, in a multiple item order, theitem allocation component may determine (based on one or more of theabove-described criteria) a sorting station to which the first inducteditem of the order is to be directed. Subsequent items of the order mayin various embodiments be automatically directed to the same sortingstation to which the first inducted item of the order was directed.

In various embodiments, the item allocation component may be configuredto generate, store, and/or maintain a dynamic data structure configuredto store information that may include but is not limited to the locationof various items and conveyance receptacles within the item fulfillmentcenter. In some cases, such information may be determined from controlsystem 190 which may include, but is not limited to, one or morecomputer systems, one or more data storage devices, one or more wiredand/or wireless networks, control system software (programs, modules,drivers, user interfaces, etc.), and one or more hand-held, mobileand/or fixed readers, scanners or scanning devices that may be able toscan, receive, or otherwise detect the marks or tags (e.g., bar codes,radio frequency identification (RFID) tags, etc.) on individual items(units) or collections of items (e.g., cases) and communicate with acontrol station or stations of the control system to, for example,determine and record the item and/or item type of the items. Thehand-held, mobile and/or fixed readers, scanners or scanning devices mayalso be able to scan, receive, or otherwise detect the marks or tags(e.g., bar codes, radio frequency identification (RFID) tags, etc.)attached to or integrated with the conveyance receptacles as well asdetermine the location of such conveyance receptacles within the orderfulfillment center. The real-time or near-real time location of suchreceptacles may in various embodiments be stored within the abovedescribed dynamic data structure.

In various embodiments, such dynamic data structure may, for eachsorting station of the order fulfillment center, include one or moremeasure of the various criteria on which the item allocation componentmay base the allocation of a given unit of an item or a conveyancereceptacle to a particular sorting station. For instance, in variousembodiments, the dynamic data structure may indicate informationincluding but not limited to whether or not a given sorting station isenabled, the available slot categorizations amongst each of the sortingstations and their associated order sorting bins, the available labor ata given sorting station, the quantity of conveyance receptacles at agiven sorting station and/or the quantity of conveyance receptaclesdestined for (e.g., en route or waiting in an item buffer) such sortingstation, the number of available slots at a given sorting station, thenumber of shipments or orders assigned to a given sorting station(whether items of such shipments are at the sorting station or en routeto the sorting station), and/or the number of occupied slots at a givensorting station. In various embodiments, the item allocation componentmay be configured to allocate a given inducted item to a particularsorting station based on information from the above-described dynamicdata structure.

Various methods may be performed by item allocation component 300 toallocate a given inducted item to a particular sorting station, someexamples of which are illustrated by the flowcharts of FIGS. 11 and 12described below. In FIG. 11, the various criteria described above areapplied in an elimination sense (e.g., sorting stations are eliminatedbased on one or more criteria) in order to determine a particularsorting station to which an inducted item is to be directed or assignedin the order fulfillment center. By performing the illustrated method,the item allocation component may balance the flow of items to thevarious sorting stations thereby avoiding gridlock and otherinefficiencies. Note that as each criterion is evaluated in theillustrated method, stations not meeting the criteria are removed fromconsideration. Also note that in various other embodiments, variousportions of the illustrated method (e.g., blocks 402-418) may beperformed according to an order different than the illustrated order.Various criteria may be added or removed from the illustrated methodwhile remaining within the spirit and scope of various embodiments.

The illustrated method begins by determining the station(s) that areenabled and ready to receive items for sortation (block 402). Asdescribed above, sorting stations may reside in an enabled or disabledstate for a variety of reasons. The method described herein may includedetermining whether a given sorting station is enabled or disabled.Typically, a sorting station is enabled if it is ready for an agent tologin or if it already has at least one agent logged in. A sortingstation may be disabled for a variety of reasons including but notlimited to repairs, routine maintenance and equipment upgrades. In othercases, some sorting stations may be disabled because order demand doesnot warrant the use of all sorting stations. In some cases, the amountof available labor or agents capable of operating a sorting station maybe less than the required amount of labor to operate all sortingstations in the order fulfillment center. In such cases, a number ofsorting stations may be left disabled until more labor becomesavailable. As indicated by block 403, if only one station is enabled,the method proceeds to block 418 where the item (and/or the conveyancereceptacle carrying the item) is assigned or directed to such station.If there are at least two remaining sorting stations, the methodproceeds to block 404.

As illustrated by block 404, the method may include determining thestation(s) that have the available slots (e.g., slots for which itemshave not already been assigned). As indicated by block 405, if only onestation has available slots, the method proceeds to block 418 where theitem (and/or the conveyance receptacle carrying the item) is assigned ordirected to such station. If there are at least two remaining sortingstations, the method proceeds to block 406.

As illustrated by block 406, the method may include determining thestation(s) that have the available slots. A given slot categorizationmay represent actual slot dimensions (e.g., 6″×6″, 12″×12″, 12″×18″,etc.) or relative slot dimensions (e.g., small, medium, large, etc.) orsome other categorization of the slot (e.g., a categorization based onvolume of the slot). In some embodiments, sorting stations may includeorder sorting bins with uniform slot categorizations (see e.g., FIGS.8A-8D) or hybrid (e.g., mixed) slot categorizations (see e.g., FIG. 8E).In various embodiments, to determine the stations that have the correctslot categorization, the method may include determining the volumetricrequirements of the order (or, alternatively, a shipment in the casethat an order is split into multiple shipments) to which the itembelongs and determining which stations have slots that can accommodatethe order's required volumetric requirements. In some case the methodmay also include determining which stations have slot categorizationthat meet best-fit requirements. For instance, in one embodiment, thebest-fit slot categorization may be the smallest slot categorizationthat is able to hold all items of the order. In some embodiments, one ormore of determinations (e.g., determination of a best-fit slot) may bemade by requesting information from a container recommender, asdescribed in more detail above. In some cases, such as if no station hasthe appropriate best-fit slot categorization available, the method maysubstitute larger slot categorizations (e.g., a “large” slot mayaccommodate a “medium” order, a “medium” slot may accommodate a “smallorder, etc.) to eliminate one or more stations. As indicated by block407, if only one station has the correct slot categorization, the methodproceeds to block 418 where the item (and/or the conveyance receptaclecarrying the item) is assigned or directed to such station. If there areat least two remaining sorting stations, the method proceeds to block408.

As illustrated by block 408, the method may include determining thestation(s) with the highest number of operators or agents manning thestation(s). In various embodiments, this may include determining thestation(s) with the highest number of operators or agents logged intothe station(s). In other cases, this may include determining thestation(s) with the highest number of operators or agents assigned thestation(s). Note that operators or agents may be assigned to a givenstation while not necessarily logged into such station (e.g., as wouldbe the case if the agent logs out of the station during a short break).Generally, the more operators at a given sorting station, the faster thestation can perform work (e.g., sort items). Accordingly, stations withlarger numbers of operators and agents are in many cases favored overstations with fewer operators or agents. As indicated by block 409, ifonly one station remains, the method proceeds to block 418 where theitem (and/or the conveyance receptacle carrying the item) is assigned ordirected to such station. If there are at least two remaining sortingstations (e.g., two or more stations are “tied” with respect to numberof operators or agents), the method proceeds to block 410.

As illustrated by block 410, the method may include determining thestation(s) with the least amount of items en route to (e.g., itemsdestined for, but yet to arrive at) the respective station. Itemsdestined for the sorting station may include items that have beeninducted but have not yet been decoupled removed (e.g., decoupled) fromtheir respective sorting bin at the sorting station. Such items mayinclude items transported by the conveyance mechanism (e.g., items onthe conveyance loop) that have not yet reached their assigned sortingstation. Such items may also include items waiting in the sortingstation's item buffer. As indicated by block 411, if only one stationhas the least amount of items en route, the method proceeds to block 418where the item (and/or the conveyance receptacle carrying the item) isassigned or directed to such station. If there are at least tworemaining sorting stations (e.g., two or more stations are “tied” withrespect to having the least amount of items en route), the methodproceeds to block 412.

As illustrated by block 412, the method may include determining thestation(s) with the least amount of incomplete shipments, which may alsobe referred to as partially sorted shipments. An incomplete order orshipment may include one or more items that are at least one item shortof being a group that includes all the items of the respective shipment.As indicated by block 413, if only one station has the least amount ofincomplete shipments, the method proceeds to block 418 where the item(and/or the conveyance receptacle carrying the item) is assigned ordirected to such station. If there are at least two remaining sortingstations (e.g., two or more stations are “tied” with respect to havingthe least amount of incomplete shipments), the method proceeds to block414.

As illustrated by block 414, the method may include determining thestation(s) with the least amount of total shipments. The number of totalshipments at a sorting station may include the number of shipments forwhich items are located at the sorting station as well as the number ofshipments for which items are en route to the sorting station (e.g., viaa conveyance mechanism, such as conveyance mechanism 200). As indicatedby block 415, if only one station has the least amount of totalshipments, the method proceeds to block 418 where the item (and/or theconveyance receptacle carrying the item) is assigned or directed to suchstation. If there are at least two remaining sorting stations (e.g., twoor more stations are “tied” with respect to having the least amount oftotal shipments), the method proceeds to block 416.

If the method reaches block 416 (e.g., at least two sorting stationsremain), the method may include applying additional criteria to theremaining sorting stations in order to determine a single sortingstation to which the item should be directed. Additionally oralternatively, the method may include randomly or pseudo-randomlyselecting one of the remaining sorting stations. Once a single sortingstation remains, the method may proceed to block 418, where the item isassigned to the remaining sorting station.

While the method of FIG. 11 utilizes the various criteria that may bedetermined by an item allocation component to eliminate all but onesorting station, the method and apparatus for managing the allocation ofitems to processing stations in an order fulfillment process may includeother methods, which are not necessarily applied in an eliminationmanner). An example of one of such methods is illustrated by theflowchart of FIG. 12. The flowchart of FIG. 12 illustrates a method thatincludes the generation of a composite score for various sortingstations and selecting the sorting station with the best (e.g., largest)score, as described in more detail below.

As indicated by blocks 500 and 530, the portions of the methodrepresented by blocks 510 and 520 may be repeated for each sortingstation of the order fulfillment center. For each sorting station, themethod may include determining one or more subscores each associatedwith an allocation criterion. In some embodiments, each subscore may beweighted (e.g., by a respective weighting value) to determine compositescore for a given sorting station. In various embodiments, suchweighting values (or simply “weights”) may each be configurable. Forexample, a weight may be configurable by a system administrator ordynamically configurable by the control system and/or item allocationcomponent. For instance, in various embodiments, as conditions withinthe material handling facility change (e.g., time of day, workloaddemand, shipment processing capacity, and any other condition of thematerials handling facility), the control system and/or item allocationcomponent may dynamically change the values of various weights inresponse to such conditions. Each allocation criterion may include anyone of the various allocation criteria described above. For example,allocation criteria may specify various requirements on one or more of:

-   -   Whether or not a given sorting station is enabled.    -   The available slot categorizations (e.g., slot sizes) amongst        each of the sorting stations and their associated order sorting        bins.    -   The available labor at a given sorting station.    -   The quantity of items (or conveyance receptacles) at a given        sorting station and/or the quantity of items (or conveyance        receptacles) en route to such sorting station (e.g., destined to        the station or waiting in an item buffer of the station).    -   The number of available slots at a given sorting station.    -   The number of shipments or orders assigned to a given sorting        station (whether items of such shipments are at the sorting        station or en route to the sorting station)    -   The number of occupied slots at a given sorting station.

In various embodiments, other types of allocation criteria may beutilized by the control system and/or the item allocation component todetermine to which sorting station a given item is to be routed. Forinstance, in one embodiment, the control system and/or item allocationcomponent may measure the number of times a sorting station operator hasmoved (e.g., from a conveyor to a sorting slot) items above a givenweight threshold (e.g., items designated as “heavy”). For example, whendetermining to which station an item having a weight above a weightthreshold (e.g., a “heavy” item) is to be sent, the control systemand/or item allocation component may select a station having operatorsthat have moved the least amount of “heavy” items within a given timeperiod (e.g., when compared to the operators of the other sortingstations). In some embodiments, the control system and/or itemallocation component may limit the amount of “heavy” items sent to agiven station or operator in accordance with health or safetyregulations.

Each subscore may be associated with a particular allocation criterion.As described above, each subscore may be configurable such that it isweighted differently than at least some of the other subscores. In somecases, each subscore may be weighted based on a designated priority. Forexample, in one embodiment, the subscore associated with whether or nota given sorting station is enabled may be weighted the most heavilywhereas other, less critical criteria may be given smaller weightings.

In various embodiments, the subscores may each represent a measureassociated with the sorting station being evaluated. For example, insome embodiments, a subscore may be a measure of available sorting slotsat the given sorting station that have a sorting slot size determined(e.g., by the control system or item allocation component) as beingbest-fit to store all items of a shipment to which the given itembelongs. In other examples, a subscore may be any of the following: ameasure of the quantity of items located at the sorting station and thequantity of items en route to the sorting station, a measure of whetherthe sorting station is enabled for use, a measure of the available laborresources at the sorting station, a measure of partially sortedshipments located at the sorting station, a measure of occupied sortingslots (e.g., slots containing at least one item of a shipment) at theparticular sorting station, a measure of partially sorted shipmentslocated at the sorting station, and/or any other measure associated withthe various allocation criteria described herein.

From each subscore, a composite score for a given sorting station may bedetermined (block 520). For example, the composite score of a givensorting station may be the sum of the various subscores determined forsuch station. In other cases, other functions or methods may be utilizedto determine the composite score. After a composite score is determinedfor each sorting station, the method may proceed to step 540 where theitem is assigned or directed to the station having the highest compositescore. Note that other methods for determining a sorting station towhich to assign or direct an inducted item may be employed. Each of suchmethods may determine a particular sorting station based on anyallocation criterion or combination of allocation criteria (as describedabove) while remaining within the spirit and scope of variousembodiments.

While the methods described above utilize various constraints (such asallocation criteria) to determine (for a given inducted item) a sortingstation to which the inducted item is to be assigned or directed, anyones of such constraints may be relaxed (or, alternatively, amplified)in various implementations while remaining with the spirit and scope ofvarious embodiments.

In various embodiments, the item allocation component described hereinmay base its assignments (at least partially) on information upstream ofthe induction point. Such information might include orders of items thatwill reach the induction point in the future, such as orders currentlyundergoing “picking” or orders even further upstream. For example, inone embodiment, the item allocation may determine that a large number ofupstream orders will require the use of “medium” slot categorizations.In such example, the item allocation component may, e.g., relax theconstraints on slot categorizations such that the item allocationcomponent (when evaluating items of “medium” orders) considers “large”slots to be the same as “medium” slots for the purpose of allocatingitems to stations. In this way, the item allocation component maypreempt any potential gridlock that might occur from an onslaught of“medium” items.

In various embodiments, the item allocation component described hereinmay assign items to sorting stations at any point during or afterinduction into the conveyance loop. In one embodiment, a readerconfigured to identify a conveyance receptacle (e.g., RFID reader,optical scanner, camera, etc.) is placed on the conveyance loop shortlyafter the induction point. In some embodiments, each time such readeridentifies a conveyance receptacle, the item allocation component may(e.g., in accordance with the various methods and techniques describedabove) assign the item to one of the sorting stations within the orderfulfillment facility. In another embodiment, the item allocationcomponent may take a “just-in-time” approach to assigning inducted itemsto sorting stations. For instance, the item allocation component maydelay the assignment for a specified time period or until the item hasreached a certain point on the conveyance loop.

In various embodiments, after the item allocation component hasdetermined a particular sorting station to which an inducted item is tobe assigned, the item allocation component may also determine aparticular slot (in an order sorting bin of the assigned station) towhich to place the item. In various embodiments, each slot may beassociated with a priority ranking (or score); the item allocationcomponent may indicate (as described above with respect to indicators158 of FIG. 6) to an agent or operator that the item is to be placed inthe slot having the highest priority (as well as a matching slotcategorization for the item's order) as determined by the allocationcomponent. In various embodiments, a slot's priority ranking may bebased on a measure of how easily an agent or operator may access theslot. For instance, a slot that is positioned at the height of anagent's torso may be easier to access than a slot that is positionedabove the agent's head or at the agent's feet.

Illustrative System

In one embodiment, a system that implements one or more components of anon-linear, unit-level sortation system as described herein may includea general-purpose computer system that includes or is configured toaccess one or more computer-accessible media, such as computer system900 illustrated in FIG. 13. In the illustrated embodiment, computersystem 900 includes one or more processors 910 coupled to a systemmemory 920 via an input/output (I/O) interface 930. Computer system 900further includes a network interface 940 coupled to I/O interface 930.

In various embodiments, computer system 900 may be a uniprocessor systemincluding one processor 910, or a multiprocessor system includingseveral processors 910 (e.g., two, four, eight, or another suitablenumber). Processors 910 may be any suitable processors capable ofexecuting instructions. For example, in various embodiments, processors910 may be general-purpose or embedded processors implementing any of avariety of instruction set architectures (ISAs), such as the x86,PowerPC, SPARC, or MIPS ISAs, or any other suitable ISA. Inmultiprocessor systems, each of processors 910 may commonly, but notnecessarily, implement the same ISA.

System memory 920 may be configured to store instructions and dataaccessible by processor(s) 910. In various embodiments, system memory920 may be implemented using any suitable memory technology, such asstatic random access memory (SRAM), synchronous dynamic RAM (SDRAM),nonvolatile/Flash-type memory, or any other type of memory. In theillustrated embodiment, program instructions and data implementingdesired functions, such as those methods and techniques described abovefor a control system 190 and/or an item allocation component 300 in anon-linear, unit-level sortation system, are shown stored within systemmemory 920 as code 925.

In one embodiment, I/O interface 930 may be configured to coordinate I/Otraffic between processor 910, system memory 920, and any peripheraldevices in the device, including network interface 940 or otherperipheral interfaces. In some embodiments, I/O interface 930 mayperform any necessary protocol, timing or other data transformations toconvert data signals from one component (e.g., system memory 920) into aformat suitable for use by another component (e.g., processor 910). Insome embodiments, I/O interface 930 may include support for devicesattached through various types of peripheral buses, such as a variant ofthe Peripheral Component Interconnect (PCI) bus standard or theUniversal Serial Bus (USB) standard, for example. In some embodiments,the function of I/O interface 930 may be split into two or more separatecomponents, such as a north bridge and a south bridge, for example.Also, in some embodiments some or all of the functionality of I/Ointerface 930, such as an interface to system memory 920, may beincorporated directly into processor 910.

Network interface 940 may be configured to allow data to be exchangedbetween computer system 900 and other devices attached to a network 800,such as other computer systems, communications devices, controlmechanisms, readers, scanners and so on that are components of thenon-linear, unit-level sortation system. The communications channels mayinclude, but are not limited to conventional and mobile telephone andtext messaging communications channels. Network interface 940 maycommonly support one or more wireless networking protocols (e.g.,Wi-Fi/IEEE 802.11, or another wireless networking standard). However, invarious embodiments, network interface 940 may support communication viaany suitable wired or wireless general data networks, such as othertypes of Ethernet network, for example. Additionally, network interface940 may support communication via telecommunications/telephony networkssuch as analog voice networks or digital fiber communications networks,via storage area networks such as Fibre Channel SANs, or via any othersuitable type of network and/or protocol.

In some embodiments, system memory 920 may be one embodiment of acomputer-accessible medium configured to store program instructions anddata as described above for FIGS. 1 through 9 for implementing a controlsystem for, or possibly other components of, a non-linear, unit-levelsortation system. However, in other embodiments, program instructionsand/or data may be received, sent or stored upon different types ofcomputer-accessible media. Generally speaking, a computer-accessiblemedium may include storage media or memory media such as magnetic oroptical media, e.g., disk or DVD/CD coupled to computer system 900 viaI/O interface 930. A computer-accessible medium may also include anyvolatile or non-volatile media such as RAM (e.g. SDRAM, DDR SDRAM,RDRAM, SRAM, etc.), ROM, etc, that may be included in some embodimentsof computer system 900 as system memory 920 or another type of memory.Further, a computer-accessible medium may include transmission media orsignals such as electrical, electromagnetic, or digital signals,conveyed via a communication medium such as a network and/or a wirelesslink, such as may be implemented via network interface 940.

Various embodiments may further include receiving, sending or storinginstructions and/or data implemented in accordance with the foregoingdescription upon a computer-accessible medium. Generally speaking, acomputer-accessible medium may include storage media or memory mediasuch as magnetic or optical media, e.g., disk or DVD/CD-ROM, volatile ornon-volatile media such as RAM (e.g. SDRAM, DDR, RDRAM, SRAM, etc.),ROM, etc. As well as transmission media or signals such as electrical,electromagnetic, or digital signals, conveyed via a communication mediumsuch as network and/or a wireless link.

The various methods as illustrated in the Figures and described hereinrepresent exemplary embodiments of methods. The methods may beimplemented in software, hardware, or a combination thereof. The orderof method may be changed, and various elements may be added, reordered,combined, omitted, modified, etc.

Various modifications and changes may be made as would be obvious to aperson skilled in the art having the benefit of this disclosure. It isintended that embodiments embrace all such modifications and changesand, accordingly, the above description to be regarded in anillustrative rather than a restrictive sense.

1.-22. (canceled)
 23. A control system for assigning a given item of aplurality of items to a particular sorting station of a plurality ofsorting stations, wherein the control system is configured to: directones of the plurality of items to ones of the plurality of sortingstations via a conveyance mechanism in which the plurality of items areinducted, wherein each sorting station comprises a plurality of sortingslots for sorting items of said plurality of items into respectiveshipments; wherein the plurality of sorting stations comprises at leastsome sorting slots of different sizes; for each given sorting station ofsaid plurality of sorting stations, determine a respective compositescore based on a plurality of determined subscores, wherein saidplurality of subscores comprises: a subscore that is a measure ofavailable sorting slots at the given sorting station that have a sortingslot size determined as being best-fit to store all items of a shipmentto which the given item belongs; a subscore that is a measure of thequantity of items located at the sorting station and the quantity ofitems en route to the sorting station; assign the given item of saidplurality of items to said particular sorting station in response todetermining that the respective composite score of said particularsorting station is larger than the composite scores of each of the othersorting stations of said plurality of sorting stations; and direct thegiven item to said particular sorting station assigned by the controlsystem.
 24. The control system of claim 23, wherein each of at leastsome of said plurality of subscores are weighted in the composite scoreby a respective weight.
 25. The control system of claim 24, wherein eachrespective weight is configurable.
 26. The control system of claim 23,wherein said plurality of subscores comprises a subscore that is ameasure of whether the given sorting station is enabled for use.
 27. Thecontrol system of claim 23, wherein said plurality of subscorescomprises a subscore that is a measure of the available labor resourcesat the given sorting station.
 28. The control system of claim 23,wherein said plurality of subscores comprises a subscore that is ameasure of partially sorted shipments located at said sorting station.29.-52. (canceled)